Name: The Fortress of the Treasure Queen
ISBN: 9780439661577

Tony Abbott

David Merrell

Eric and his friends have to stop Ko from using a lightning-powered submarine found in the fortress of the Treasure Queen to destroy Jaffa City, but they can't do it without the help of their old enemy, Lord Sparr.

The Fortress of the Treasure Queen

Kirsten Simkiss

** spoiler alert **
           This one you can read out of order and still enjoy it. Obviously, things carried over from previous books, but it does a good job of explaining what was happening. Provided you read at least the first book maybe some in the middle of the series, you'd probably do well. This one takes place after Sparr has been turned back into a child. 

As always, the world is very inventive. Perhaps not as inventive as some of the other books, but it's always fun to see a pretty-in-pink ruler go from happy and plump to horrifying and wraith-like.